Janet Jackson

Donald Elson, Kosta Trouva

Howie Mandel, Juliette Lewis

Denzel Washington, Hilary Duff

Tom Felton, Ne-Yo

David Arquette, Ashley Greene, Billy the Exterminator

Billy Bob Thornton, Kunal Nayyar, Ice Cube

Dwayne Johnson, Katie Cassidy

Jennifer Love Hewitt

Bill Cosby, Angela Kinsey, Atomic Tom

Charles Barkley, Brandy, Cee-Lo Green

Mario Lopez

Khloe Kardashian, Jo Frost, Nicki Minaj

Bob Saget, Nene Leakes, Keri Hilson

Alan Cumming, Chris D'Elia

Steve Harvey, the 88

Eric Stonestreet, J.B. Smoove, Dov Davidoff

Anna Faris, Apolo Anton Ohno, Natasha Bedingfield

Mila Kunis, Dr. Drew Pinsky, Chrisette Michele

Justin Timberlake, Stephen Dorff, Ciara

Xzibit, a performance from Cirque Du Soleil's "Mystere"

Gene Simmons, Scott Bakula, Bettye Lavette with the Ese Vatos

Ron Artest, will.i.am, Dean Cole

Jack Black, Hailee Steinfeld, Filter

Lauren Graham, Will Sasso, Plain White T's

Mary Lynn Rajskub, Maz Jobrani

El Debarge featuring Faith Evans, Michael Bearden & the Ese Vatos

David Duchovny, Kristen Schaal, Saving Abel

Seth Rogen, Ginnifer Goodwin, Sick Puppies

William H. Macy, Camille Grammer, Cali Swag District

Cameron Diaz, Jason Priestley, Luke Perry, Greg Fizsimmons

Bill Engvall, Johnny Weir, My Chemical Romance

Ashley Tisdale, Kevin Hart, Grace Potter & the Nocturnals

Vanessa Williams, Shorty Rossi

Jason Statham, Busy Philipps, Wiz Khalifa

Jennifer Love Hewitt, Guy Fieri

Kristen Bell, Jake Johnson, Slash

DeSean Jackson, the Thermals

Mindy Kaling, Derek Fisher, Jasper Redd, Arturo Sandoval

Billy Gardell, Rachel Bilson, OK Go

Jamie Foxx, Aubrey Plaza

Channing Tatum, Margaret Cho, 50 Cent with Governor

Joan Rivers, Greg Jennings, Baron Vaughn

Brad Womack, Taylor Momsen, the Pretty Reckless

R. Kelly, Paul Wesley, James Loney, Bobby Castillo, Tommy Davis, Kenny Landreaux, Rudy Law, Steve Lyons, Don Mattingly

Justin Bieber, Far East Movement

Liam Neeson, a performance by the Broadway cast of "Rock of Ages"

200th Episode - Jenni "JWoww" Farley, Jim Jefferies

Amar'e Stoudemire, Kate Gosselin, Sebastian Maniscaclo

Martin Lawrence, Jared Leto, 30 Seconds to Mars

Forest Whitaker, Jessica Lucas, Bobby V & Bobby Brown

Jason Biggs, Anne Heche

Owen Wilson, Aly Michalka, Terry Fator

Cheryl Burke, Brandon T. Jackson, John Popper & the Duskray Troubadours

Ron Artest, DJ Pauly D, Michelle Rodriguez, Future Funk

Topher Grace, Scott Disick, Cake

Forest Whitaker, Donald Glover, Steel Train

Aaron Eckhart, Malin Akerman, Eric Andre

Curtis Stone, Lupe Fiasco

Pee-wee Herman, Emanuelle Chriqui

Mike Tyson, Emmy Rossum, 30 Seconds to Mars

Jim Rome, Boney James

Matthew McConaughey, Micky Ward, Ron Artest featuring George Lopez, Fat Joe, B Real, Lenny and Max from Aventura and Taz

Bethenny Frankel, D.L. Hughley, Seether

Vanessa Hudgens, Sergio Mendes

Larry King, Brent Weinbach

Snoop Dogg, Brittany Snow

Lil Jon, Panic! At The Disco

Drew Carey, Sarah Shahi, Quinn Dahle

Lisa Lampanelli

Danny McBride, Camilla Luddington, Avril Lavigne

Kathy Griffin, Tom Felton